The present invention relates to a tire noise reducing system, more particularly to a noise damper which is disposed on a pneumatic tire or wheel rim facing the tire cavity.
As is well known, when a pneumatic tire is mounted on a wheel rim, the tire hollow forms a closed annular cavity filled with air. During running the air is excited by vibrations and resonance is caused at specific frequencies depending on the size of the cavity. Such resonance worsens the running noise from the tire.
It was known that such a resonance noise can be reduced by putting a sponge-like material into the cavity. However, if a big damper is used in order to completely reduce the resonance noise, even if the damper is made of a light sponge-like material, the wheel is liable to lose its rotational balance. This is particularly remarkable when the damper contacts with the tire inside.
It is therefore, an object of the present invention to provide a noise reducing system including a noise damper being capable of achieving a maximum noise reduction with a minimum damper size.
According to one aspect of the present invention, a tire noise reducing system includes:
a pneumatic tire,
a wheel rim on which the pneumatic tire is mounted, and
a noise damper disposed in a cavity, the cavity formed between the rim and tire when mounted as being surrounded by the tire and rim,
wherein the noise damper is made of a porous material having a specific gravity of from 0.005 to 0.06 and is secured on a surface facing the cavity, and
the volume S2 of the noise damper is in a range of from 0.4 to 20.0% of the volume S1 of the cavity.
Preferably, the noise damper is provided with an uneven surface or an outer layer for less sound reflection facing the cavity. The undermentioned shape index E of the noise damper is more than 1, and the ratio T/W of the thickness T to the width W of the damper is not less than 1.